This invention relates to character reading apparatus.
Character reading apparatus with a hand-held scanner have been used for the purpose of reducing the time required for producing bills at the counter of department stores, supermarkets and other retail shops and stores, preventing misinputs due to erroneous keying and realizing automation of account and stock keeping. The apparatus have a photoelectric converter, which is manually operated to scan, for instance, a line of characters printed on a price card for optically reading these characters. The identified character data thus obtained from the apparatus may be automatically fed to a POS system or the like.
When operating this sort of character reading apparatus, the hand-held scanner having a photoelectric converter has to be manually operated for scanning price card, and the scanning speed is not fixed. In order to obtain accurate character pattern data irrespective of fluctuations of the scanning speed and thus simplify the following character identification process, it has been in practice to use as the photoelectric converter an area scanner having a matrix array of photoelectric converting elements (as disclosed, for instance, in U.S. Pat. No. 3,964,022).
In the optical character reading apparatus as disclosed in U.S. Pat. No. 3,964,022, the identification circuit is comprised of a logic circuit for extracting the features of characters. In this arrangement, the identification of the characters can be performed at high speeds. However, where the number of characters to be identified is desired to be increased or where the form or type of the character is changed, there is inconvenience that the logic circuit has to be redesigned. On the other hand, a similarity method or pattern matching method is known as an identification system of the conventional mechanical scan type character identification apparatus as is disclosed in U.S. Pat. No. 3,688,267. According to the similarity method, where there is involved an increase in the number of the characters to be identified or a change in the form of the characters, this situation can be easily coped with by merely changing the standard pattern data for the dictionary. If, however, the similarity method is used, there is a problem that a longer time is required for the identification of one character than in U.S. Pat. No. 3,964,021.
For obtaining reliable identification of a character in a short period of time, it is desired to execute the identification process for character pattern data that is obtained when the light receiving area of the photoelectric converter is located substantially at the center of the corresponding character pattern. For this reason, the identification process for character data is executed when it is confirmed that when incident light data of a character pattern are detected the height and width directions thereof and that the data contains the whole character pattern data of the character to be identified and no trace of the pattern of an adjacent character. In this case, the space between adjacent characters is concurrently detected on the basis of the projection data in the width direction of character. When the space is detected, character pattern data concerning the next character is subjected to identification process. However, when a line of characters is scanned obliquely with the area scanner, when a character line contains characters of a greater size than the proper size, when there is an ink stain or spot in the inter-character space or when there are fluctuations of ink density of printed characters, it is impossible to obtain reliable detection of the inter-character space. Therefore, with the prior-art character reading apparatus dropout of character and repeated reading of the same character a plurality of times are liable, and this is undesired from the standpoint of the reliability of reading.
In a further aspect, since the character identification process takes considerable time, it has been in usual practice to execute identification process for the first character pattern, which is obtained after the detection of an inter-character space and satisfies the afore-mentioned predetermined condition. However, there is a possibility that a character pattern having a superior state to the first detected effective character pattern will be subsequently be found. Of course, the reliability of the character reading apparatus can be increased if it is arranged such that the identification process is executed for a character pattern in the most satisfactory state.